(Tcl) SharePoint -- Get Server Form Digest Value

Demonstrates how to get a server form digest value to be placed in the X-RequestDigest HTTP request header for POST, PUT, MERGE, and DELETE requests. A form digest value is typically valid for 1800 seconds (i.e. 30 minutes). This example persists the value to a file, and only requests a new form digest value if the existing one is near expiration.

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load ./chilkat.dll

# This requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

# First, let's see if we already have a persisted form digest value
# that hasn't yet expired.
set fac [new_CkFileAccess]

set xml [new_CkXml]

# My example code (below) persists the form digest XML in this format:
# 
# 	<savedFormDigestValue>
# 	<d:ExpireDateTime>2017-04-12T20:46:39Z</d:ExpireDateTime>
# 	<d:FormDigestValue>0x3059FFB920651834540F3E6792EA73F5746B302E953FF4E808E485DB1E6C2836C7CF924644995F092453B02A94DE14A7962674B7B16780AF16EAFB8C246BCDC7,12 Apr 2017 17:08:22 -0000</d:FormDigestValue>
# 	</savedFormDigestValue>
# 

set dtExpire [new_CkDateTime]

set dtNow [new_CkDateTime]

set formDigestXmlFile "qa_data/sharepoint/savedFormDigestValue.xml"
if {[CkFileAccess_FileExists $fac $formDigestXmlFile] == 1} then {

    CkXml_LoadXmlFile $xml $formDigestXmlFile

    # Get the expire date/time
    CkDateTime_SetFromTimestamp $dtExpire [CkXml_getChildContent $xml "d:ExpireDateTime"]

    # Get the current date/time
    CkDateTime_SetFromCurrentSystemTime $dtNow

    # Get both times as Unix time values
    set tNow [CkDateTime_GetAsUnixTime $dtNow 0]
    set tExpire [CkDateTime_GetAsUnixTime $dtExpire 0]

    # If tNow >= tExpire, then fall through.
    # Otherwise, just use the cached digest value.
    if {$tNow < $tExpire} then {
        puts "Cached digest value is not yet expired."
        puts "X-RequestDigest: [CkXml_getChildContent $xml d:FormDigestValue]"
        delete_CkFileAccess $fac
        delete_CkXml $xml
        delete_CkDateTime $dtExpire
        delete_CkDateTime $dtNow
        exit
    }

}

# If we got to this point, the cached digest value either does not exist, or expired.

set http [new_CkHttp]

# If SharePoint Windows classic authentication is used, then set the 
# Login, Password, LoginDomain, and NtlmAuth properties.
CkHttp_put_Login $http "SHAREPOINT_USERNAME"
CkHttp_put_Password $http "SHAREPOINT_PASSWORD"
CkHttp_put_LoginDomain $http "SHAREPOINT_NTLM_DOMAIN"
CkHttp_put_NtlmAuth $http 1

# The more common case is to use SharePoint Online authentication (via the SPOIDCRL cookie).
# If so, do not set Login, Password, LoginDomain, and NtlmAuth, and instead
# establish the cookie as shown at SharePoint Online Authentication

# When creating, updating, and deleting SharePoint entities, we'll need
# to first get the server's form digest value to send in the X-RequestDigest header.
# This can be retrieved by making a POST request with an empty body to
# http://<site url>/_api/contextinfo and extracting the value of the
# d:FormDigestValue node in the XML that the contextinfo endpoint returns.

# Apparently, SharePoint needs an "Accept" request header equal to "application/xml",
# otherwise SharePoint will return an utterly incomprehensible and useless error message.
set savedAccept [CkHttp_accept $http]
CkHttp_put_Accept $http "application/xml"

# Note: The last argument ("utf-8") is meaningless here because the body is empty.
# resp is a CkHttpResponse
set resp [CkHttp_PostXml $http "https://SHAREPOINT_HTTPS_DOMAIN/_api/contextinfo" "" "utf-8"]
if {[CkHttp_get_LastMethodSuccess $http] != 1} then {
    puts [CkHttp_lastErrorText $http]
    delete_CkFileAccess $fac
    delete_CkXml $xml
    delete_CkDateTime $dtExpire
    delete_CkDateTime $dtNow
    delete_CkHttp $http
    exit
}

# Restore the default Accept header
CkHttp_put_Accept $http $savedAccept

if {[CkHttpResponse_get_StatusCode $resp] != 200} then {
    # A response status code not equal to 200 indicates failure.
    puts "Response status code = [CkHttpResponse_get_StatusCode $resp]"
    puts "Response body:"
    puts [CkHttpResponse_bodyStr $resp]
    delete_CkHttpResponse $resp

    delete_CkFileAccess $fac
    delete_CkXml $xml
    delete_CkDateTime $dtExpire
    delete_CkDateTime $dtNow
    delete_CkHttp $http
    exit
}

CkXml_LoadXml $xml [CkHttpResponse_bodyStr $resp]
delete_CkHttpResponse $resp

# The response XML looks like this:

# <?xml version="1.0" encoding="utf-8" ?>
# <d:GetContextWebInformation xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices" xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns:georss="http://www.georss.org/georss" xmlns:gml="http://www.opengis.net/gml" m:type="SP.ContextWebInformation">
#     <d:FormDigestTimeoutSeconds m:type="Edm.Int32">1800</d:FormDigestTimeoutSeconds>
#     <d:FormDigestValue>0x3059FFB920651834540F3E6792EA73F5746B302E953FF4E808E485DB1E6C2836C7CF924644995F092453B02A94DE14A7962674B7B16780AF16EAFB8C246BCDC7,12 Apr 2017 17:08:22 -0000</d:FormDigestValue>
#     <d:LibraryVersion>15.0.4569.1000</d:LibraryVersion>
#     <d:SiteFullUrl>https://SHAREPOINT_HTTPS_DOMAIN</d:SiteFullUrl>
#     <d:SupportedSchemaVersions m:type="Collection(Edm.String)">
#         <d:element>14.0.0.0</d:element>
#         <d:element>15.0.0.0</d:element>
#     </d:SupportedSchemaVersions>
#     <d:WebFullUrl>https://SHAREPOINT_HTTPS_DOMAIN</d:WebFullUrl>
# </d:GetContextWebInformation>
# 

# Cache the digest value, and also an expiration time.  If this code is run again
# before the digest expires, we'll just get it from the file.
set xml2 [new_CkXml]

CkXml_put_Tag $xml2 "savedFormDigestValue"
CkXml_NewChild2 $xml2 "d:FormDigestValue" [CkXml_getChildContent $xml "d:FormDigestValue"]

set timeoutInSec [CkXml_GetChildIntValue $xml "d:FormDigestTimeoutSeconds"]
puts "Timeout in seconds = $timeoutInSec"

# Convert this to an expire timestamp.
# Let's make it expire 30 seconds prior to the actual timeout, just to be safe.
if {$timeoutInSec > 30} then {
    set timeoutInSec [expr $timeoutInSec - 30]
}

CkDateTime_SetFromCurrentSystemTime $dtExpire
CkDateTime_AddSeconds $dtExpire $timeoutInSec
CkXml_NewChild2 $xml2 "d:ExpireDateTime" [CkDateTime_getAsTimestamp $dtExpire 0]

# Persist the digest and expire time to a file.
CkXml_SaveXml $xml2 $formDigestXmlFile

puts "Here is the new form digest value:"
puts "X-RequestDigest: [CkXml_getChildContent $xml d:FormDigestValue]"

delete_CkFileAccess $fac
delete_CkXml $xml
delete_CkDateTime $dtExpire
delete_CkDateTime $dtNow
delete_CkHttp $http
delete_CkXml $xml2